WASHINGTON (AP) - Military leaders said Tuesday that sexual assault in the ranks is "like a cancer" that could destroy the force, but they expressed serious concerns about far-reaching congressional efforts to strip commanders of some authority in meting out justice.

In an unusual joint appearance, Army Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, and the head of each branch of the military testified on what is widely viewed as an epidemic of sexual assault plaguing the services.

Outraged by high-profile cases and overwhelming statistics, lawmakers have moved aggressively on legislation to address the scourge of sexual assault.

Sen. Carl Levin, D-Mich., chairman of the Armed Services Committee, said the problem of sexual assault "is of such a scope and magnitude that it has become a stain on our military."

Congress has acted in prior years to ensure the aggressive investigation and prosecution of sexual assaults, Levin said, but more needs to be done. The committee is considering seven bills to deal with sexual assault.

As important as additional protections would be, Levin said, the problem won't be addressed successfully without a cultural change throughout the military. And that starts at the top of the chain of command.

"The military services are hierarchal organizations: The tone is set from the top of that chain, the message comes from the top, and accountability rests at the top," said Levin, who has not endorsed any of the bills.

The military leaders offered no disagreement about the impact on the services.

"Sexual assault and harassment are like a cancer within the force - a cancer that left untreated will destroy the fabric of our force," said Army Gen. Ray Odierno. "It's imperative that we take a comprehensive approach to prevent attacks, to protect our people, and where appropriate, to prosecute wrongdoing and hold people accountable."

While acknowledging the problem and accepting that legislation is inevitable, military leaders insisted that commanders keep their authority to handle sexual assault cases.

"Reducing command responsibility could adversely affect the ability of the commander to enforce professional standards and ultimately, to accomplish the mission," Dempsey told the committee.

Sen. Kirsten Gillibrand, D-N.Y., a member of the committee, is a proponent of ambitious legislation that would remove commanders from the process of deciding whether serious crimes, including sexual misconduct cases, go to trial. That judgment would rest with seasoned trial counsels who have prosecutorial experience and hold the rank of colonel or above.

The Pentagon estimated in a recent report that as many as 26,000 military members may have been sexually assaulted last year, up from an estimated 19,000 assaults in 2012, based on an anonymous survey of military personnel. While the number of sexual assaults that members of the military actually reported rose 6 percent to 3,374 in 2012, thousands of victims were still unwilling to come forward despite new oversight and assistance programs aimed at curbing the crimes, the report said.

Sen. Barbara Mikulski, D-Md., a co-sponsor of the Gillibrand bill and chairwoman of the Senate Appropriations Committee, called the legislation "bold" and "out of the box." She dismissed concerns that it goes too far in overhauling the military justice system, saying it's time to try a new approach to solving a problem that has persisted for years.

"I think 26,000 sexual assaults is going too far," Mikulski said. "And now there is even a criminal investigation of the football team at the Naval Academy, where we are training the next best."

"This is a problem for the military," Sen. Claire McCaskill said on CBS' "This Morning" Tuesday.

The Missouri Democrat said, "You know, they're like 20 years behind. They thought they could train their way out of this problem."

A steady drumbeat of high-profile cases combined with the most recent statistics from the Pentagon have spurred Congress to move aggressively on legislation to deal with sexual assault in the military.

Last week, the Pentagon said the U.S. Naval Academy is investigating allegations that three football team members sexually assaulted a female midshipman at an off-campus house more than a year ago. A lawyer for the woman says she was "ostracized" on campus after she reported it.

In recent weeks, a soldier at the U.S. Military Academy was charged with secretly photographing women, including in a bathroom. The Air Force officer who led the service's Sexual Assault Prevention and Response unit was arrested on charges of groping a woman. And the manager of the Army's sexual assault response program at Fort Campbell, Ky., was relieved of his post after his arrest in a domestic dispute with his ex-wife.

Oklahoma Sen. James Inhofe, top Republican on the committee, said he was wary of proposals to restrict the authority of commanders to discipline their troops.

"To take the commander out of the process will invite failure," Inhofe said in a speech on the Senate floor Monday. "These commanders have to make decisions to send our brave troops into battle. How ludicrous is it that we would say to our commanders, 'You've got to make a decision to send one of our kids into battle where they may end up losing their life, but you can't participate in the justice system of the troops.' It doesn't make any sense at all."

Gilibrand's legislation has 18 co-sponsors, including four Republicans.

In the House, Reps. Michael Turner, R-Ohio, and Niki Tsongas, D-Mass., have crafted legislation that would establish dismissal or dishonorable discharge as the mandatory minimum sentence under military law for service members found guilty of rape, sexual assault, forcible sodomy or an attempt to commit those offenses. Commanders also would be barred from reducing or commuting the minimum sentence except in situations in which the accused substantially aided the government in the investigation or prosecution of another assailant.

Their bill, however, stops short of taking those cases outside the military chain of command.

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